Measurement of vegetation coverage on a small scale is the foundation for the monitoring of changes in vegetation cover-age and of the inversion model of monitoring vegetation coverage on a large scale by remote sensing. Using the object-oriented ana-lytical software, Definiens Professional 5, a new method for calculating vegetation coverage based on high-resolution images (aerial photographs or near-surface photography) is proposed. Our research supplies references to remote sensing measurements of vegeta-tion coverage on a small scale and accurate fundamental data for the inversion model of vegetation coverage on a large and interme-diate scale to improve the accuracy of remote sensing monitoring of changes in vegetation coverage.
A non-dimensional relative sensitivity coefficient was employed to predict the responses of reference crop evapotranspiration (ET0) to perturbation of four climate variables in Tao'er River Basin of the northeastern China. Mean monthly ET0 and yearly ET0 from 1961 to 2005 were estimated with the FAO-56 Penman-Monteith Equation. A 45-year historical dataset of average monthly maximum/minimum air temperature, mean air temperature, wind speed, sunshine hours and relative humidity from 15 meteorological stations was used in the analysis. Results show that: 1) Sensitivity coefficients of wind speed, air temperature and sunshine hours were positive except for those of air tem- perature of Arxan Meteorological Station, while those of relative humidity were all negative. Relative humidity was the most sensitive variable in general for the Tao'er River Basin, followed by sunshine hours, wind speed and air tem- perature. 2) Similar to climate variable, monthly sensitivity coefficients exhibit large annual fluctuations. 3) Sensitivity coefficients for four climate variables all showed significant trends in seasonal/yearly series. Also, sensitivity coefficients of air temperature, sunshine hours and wind speed all showed significant trends in spring. 4) Among all sensitiv- ity coefficients, the average yearly sensitivity coefficient of relative humidity was highest throughout the basin and showed largest spatial variability. Longitudinal distribution of sensitivity coefficients for air temperature, relative hu- midity and sunshine hours was also found, which was similar to the distribution of the three climate variables.
The upper and middle reaches of the Taoer River,a representative ecologically sensitive area,has experienced great climate change and rapid agricultural and industrial development since 1961.There is therefore an urgent need to evaluate the impact of climate change and human activities on stream flows to serve better the water resource management in this region.The nonparametric Mann-Kendall test and moving t-test were used to identify trends and change points in stream flow,precipitation and potential evapotranspiration data series.A significant upward trend has been found in annual stream flow,with an abrupt change identified in 1985 at the Taonan station which is the station that controls the entire study area.The stream flow data was divided into a baseline period and a period of change.Both Fu and Zhang's functions were employed to evaluate the impacts of variation in climate and human activities on mean annual stream flow,based on precipitation and potential evaporation.Analysis of the increase in mean annual stream flow between the baseline and the period of change indicated that climate change accounted for about 45% of the total increase and human activities were responsible for about 55%.
